Welcome to the forum!
The job requirements vary greatly for welding depending upon what type of industry you get into such as fabrication, construction, inspection etc. The requirements can then vary within each of those groups depending upon what type of welding you do, structural, automated, pipe, tube etc..
In the construction field you can experience cramped condition, high temperatures, working at heights, random periods with no work, lots of travel, and good pay.
Fabrication is usually less demanding as far as the work conditions go and that is usually reflected in the pay.
In my experience pipe/tube welders have more opportunities for work than others but that may depend on the industry in your area.
Many trade unions have welding and very good training programs. Some may even give you credit for previous hours worked to apply towards your apprenticeship. I have welded for years and even though I entered the boilermakers union as an apprentice, I make more money per hour than any non-union job I have worked as a journeyman on my tools. Thats NOT including benefits.
My 1st visit to the doctor in which I had completely paid health insurance was a month or so ago and I can tell you that the benefits are quite valuable too.
There are many opportunities for welding but they range from very low paying entry level position and up. Theres not a magic course you can take to get to the top but education/training and experience will add up to quite a rewarding career.
Regardless of what sector you go into and whether it be union or non-union it is a higly respected trade that requires skills unlike any other craft you may come across. If you enjoy your job, you will prosper at it. (That doesn't always mean "make alot of money".)
I hope the best for you
Gerald Austin